This patent application relates to and incorporation herein by reference Japanese Patent Applications No. 11-245381 filed on Aug. 31, 1999, No. 11-247316 filed on Sep. 1, 1999 and No. 11-249025 filed on Sep. 2, 1999.
This invention relates to a vital signal detecting apparatus for detecting a vital signal, having an attachable device to be attached for example to a finger, an ear, an arm, a leg, torso or a neck of a human subject.
There have been vital signal detecting apparatuses, as disclosed, for instance, in JP-A-8-266493 or Electronic Data Communications Society, Technical Report 1995-06. To check a vital signal (such as a pulse wave), a human subject has to operate an on/off switch himself or herself. If the subject operates the on/off switch without inserting a finger into the attachable device, because a sensor picks up external noise and outputs an abnormal signal, the vital signal checking device erroneously determines that the subject is abnormal. Further, if a ring part of a pulse wave sensor fails even slightly to match the size (thickness) of the finger, it is difficult for a detecting part to be kept in contact with the surface of the finger. Thus, extraneous light, for example, sunlight or light from fluorescent lights, affect the measurement.
There have also been vital signal detecting apparatuses, used when a vital signal (such as the pulse wave) of for example an elderly or infirm subject is to be monitored over a long period, with which an attachable device is attached for instance to an arm or a leg of the subject and a vital signal detected by a sensor is transmitted to a vital signal checking device by radio waves or the like. If the elderly or infirm subject removes the attachable device, because the sensor picks up external noise and transmits an abnormal signal to the vital signal checking device, again the vital signal checking device erroneously determines that the subject is abnormal.
It is therefore an object of the present invention to provide a vital signal detecting apparatus which eliminates problems caused by abnormal vital signals detected when an attachable device is not attached.
According to the present invention, a vital signal detecting apparatus comprises an attachable device to be attached to a finger, a sensor having a light-emitting device and a light-receiving device, and a transmitting circuit for transmitting a signal waveform as a pulse wave from the sensor to a pulse wave monitoring unit.
Preferably, the vital signal detecting unit also has an attachment detecting circuit for detecting whether or not the attachable device is in an attached state by comparing a signal waveform obtained when the light-emitting device is on with a signal waveform obtained when the light-emitting device is off and an operation control circuit for controlling the operation of the sensor, the transmitting circuit and the attachment detecting circuit.
Preferably, the light-transmitting plate is disposed above the light-emitting device and the light-receiving device to pass light therethrough, and the light transmitting plate may be an IR-cut filter capable of blocking light of wavelengths greater than 700 nm.